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A BOOK

OF

BIOTECHNOLOGY

Chapt er

Chapter

13

TRACER TECHNIQUE—THE USE

OF ISOTOPES AS TRACERS

INTRODUCTION

The atoms of most chemical elements exist in more than one variety. Each kind of a given element has a different atomic weight, but all of them carry the same nuclear charge. For example, there are three different kinds of magnesium atoms with atomic weights of 24, 25, and 26 respectively. Such different varieties of atoms of a given element are called isotopes.

Differences in the chemical behaviour of two isotopes of the same element are so slight as to be barely detectable, and ordinarily they cannot be separated by chemical methods. The chemical properties of all isotopes of a given element are virtually identical, because all have the same electronic configuration ; one isotope differs from another only in the constitution of the atomic nucleus which is composed of protons and neutrons.

RADIOACTIVE ISOTOPES

In addition to the stable isotopes described above, there are many radioactive isotopes of certain heavy elements such as uranium and radium occur in nature. The atoms of many elements not normally radioactive may be made so by bombardment with various types of elementary particles such as neutrons, protons, deutrons, and alpha particles. Such bombardments are usually accomplished with the aid of a cyclotron or a uranium pile reactor.

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A BOOK

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Chapter

PROTEINS

AND

9

NUCLEIC ACIDS

INTRODUCTION

The chemistry of nucleic acids, as expressed through the proteins, regulates the intricate biochemical properties of life and the dynamics of evolution. A most significant influence of proteins resides in the fact that many are functionally active as enzymes. The enzymes are vital for the rapid rate of biochemical reactions. Although many biochemical reactions will proceed to completion in the absence of enzymes, these reactions are extremely slow. Indeed, we could go so far as to say that enzymes and life are inseparable.

Two other important functions of proteins are as major natural hydrogen ion buffers and structural components of cells. Certainly many important characteristics of proteins led scientists to the chemistry of regulators of cellular information, the nucleic acids.

AMINO ACIDS AND AMIDES

The acid hydrolysis of protein molecule reveals that it is composed of smaller repeating units, the amino acids. With the exception of two secondary amino acids, the amino acids found in protein have the following general structure.

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Chp-12

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A BOOK

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BIOTECHNOLOGY

Chapt er

Chapter

12

CHROMATOGRAPHY

INTRODUCTION

Chromatography is an analytical technique for separating two or more chemical compounds in solution by taking advantage of the fact that they are removed from solution at different rates when the latter is percolated down a column of a powdered adsorbent or passed across the surface of an absorbent paper. This is one of the most significant and reliable methods used in the fields of chemistry and biological sciences to obtain and identify substances (such as proteins, chlorophyll pigments, etc.), in a high state of purity.

Chromatography, a term derived from the Greek words chroma, colour, and graphien, to record, was introduced by the Russian botanist Michael Tswett in 1906. He described the separation of a mixture of leaf pigments on a column of calcium carbonate.

CHROMATOGRAPHIC METHODS

In all the chromatographic techniques, difference in affinity involves the process of adsorption, or partition. In adsorption, the binding of a compound, to the surface of the solid phase takes place. In partition the relative solubility of a compound in two phases, results in the partition of the compound in two phases.

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Chp-6

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Chapt er

Chapter

6

MYCORRHIZAE

INTRODUCTION

The root hairs and other surfaces of the young root do not constitute the chief absorbing surfaces in all plants. Exceptions to this situation are found in a number of kinds of plants in which the young, active portions of the roots are invaded by specific soil fungi. The resulting association is intimate and complex, and the combination of root and fungus is termed as a mycorrhiza (literally, “fungus root”).

WHAT IS A MYCORRHIZA ?

A mycorrhiza is mutualistic morphological and physiological association between a fungus and the root of some species of higher plant. These structures are formed as a result of the invasion of young roots by the hyphae of various species of fungi commonly found in forest soils.

It is likely that the great majority of land plants enter into this kind of relation with soil fungi. The mycorrhizal fungi are present in forest soil and become associated with seedlings that germinate there. Seedlings growing elsewhere frequently do not thrive because of the lack of mycorrhizae.

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